| 摘要 |
<p>The electrical resistance is housed in a composite body made of a material which is a good heat conductor, externally insulated so as not to leak heat into the external environment and machined in any way so that it comprises internally at least two separate and offset channels (4, 5) having identical dimensional characteristics and having essentially equal surface areas of contact with the resistance and essentially equal coefficients of heat exchange and that are provided with respective inlet ports (112, 113) and with respective outlet ports (118, 119), the inlet ports being connectable as required through switching-valve means (16) to the source (17) supplying the compressed air for heating, while the two discharge ports of the said channels are connected, one to the utilizing appliance (21), for example to the heating unit, to the sealing unit, to the cutting station or to another cyclically operated utilizing appliance and the other discharge port is connected to an exhaust duct (19) that ends in any position remote from the said utilizing appliance, the whole in such a way that by supplying one or other of the said channels with the stream of compressed ambient air, the compressed hot air produced by the generator can be sent to the utilizing appliance or to the said exhaust duct while maintaining unchanged heat exchange conditions between the resistance and the stream of air whatever path the air flows, owing to the structural identity and to the uniformly distributed offset locations of the said channels.</p> |
